1. Field of the Invention
The present invention generally relates to an image forming apparatus applying an internal bus interface technology and a data transmission technology, apparatuses applying a control and communication method and functioning as a printer, a digital copier, or the like.
2. Description of the Related Art
Japanese Laid-open Patent Application No. 2001-16382 discloses that a high flexible system can be provided by using a high-speed serial interface as an internal interface of an image forming apparatus.
FIG. 1 is a block diagram showing a configuration of an image forming apparatus based on a conventional bus technology. An input scanner 11 functioning as an input module such as a scanner scanning an image, an output plotter 12 functioning as an output module for outputting an image, and a CPU 13 (process A) and an ASIC (Application Specific Integrated Circuit) 14 (process B) as process modules for conducting various image processes conducting an input to an output are connected to a main memory 15 via a common bus 16.
Since each of the process modules 13 and 14 conducts a data transmission via the common bus 16, while one process module uses the main memory 15, another process module cannot access the main memory 15 and is required to wait until the main memory 15 becomes available. A buffer memory may be prepared at a module side in order to process until the common bus 16 becomes available. However, accompanying with higher speed, a capacity required to the buffer memory increases. Also, since the common bus 16 covers all processes, data transmission process ability with a remarkable higher rate is required.
Accompanying with higher speed and higher quality of the image forming apparatus, in the data transmission technology inside the image forming apparatus, a high speed and a real-time process are required further more. Conventionally, a bus technology such as a PCI (Peripheral Component Interconnect) has been used for the internal data transmission. In this bus technology, a plurality of modules use the common bus by a time-sharing. In an image apparatus which requires to conduct various processes simultaneously by a pipeline method, a capacity required to the buffer memory is increased in response to an improvement of the speed. Thus, it becomes further difficult to maintain the real-time operation and conventional bus technologies are not suitable for these current requirements.
FIG. 2 is a schematic diagram illustrating a connection aspect between units in a conventional image forming apparatus. As shown in FIG. 2, units in a conventional copier and a conventional composite apparatus are directly connected to each other by a dedicated bus. The conventional copier having a single function as a copier conducts a filtering process with respect to image data read by a scanner unit 21 to convert a color by a scanner image process unit 22 and transfers the image data to a plotter image process unit 24 via a dedicated bus 20.
The plotter image process unit 24 sends data to a plotter unit 25 after conducting various filtering processes and corrections to bring out process characteristics of a plotter, and forms an image by the plotter unit 25.
FIG. 3 is a schematic diagram illustrating another connection aspect between units in the conventional image forming apparatus. Recently, the conventional image forming apparatus has been improved as a composite apparatus to include a copier. Accordingly, the number of units is increased and a configuration using a general purpose bus 20a has been used. For example, as shown in FIG. 3, a scanner unit 21a, a scanner image process unit 22a, a plotter control unit 23a, a plotter image process unit 24a, and a plotter unit 25a are connected to the general purpose bus 20a. By using the general purpose bus 20a, a scalability of functions of the image forming apparatus is increased.
As technologies related to the convention image forming apparatus above-described, the Japanese Laid-open Patent Application No. 2001-16382 discloses a digital copier and a digital copier system capable of configuring a higher flexible system by using a high speed serial interface as an internal interface. According to the Japanese Laid-open Patent Application No. 2001-16382, a LDU for controlling a write laser for writing an image onto a photoreceptor, a SCU for controlling a scanner, and a PCU for controlling an operation panel used by a user who inputs an operation instruction are directly connected to an MBD for controlling the entire digital copier by a serial cable via a high-speed serial interface.
However, the number of requests for a higher speed of the image forming apparatus has been increased, the data transmission cannot be conducted at a sufficiently high-speed by using the general bus. Moreover, it becomes further difficult to maintain the scalability of the image forming apparatus by electrical and physical constraints of hardware. Furthermore, in order to maintain transmission speed and scalability, it requires increasing a bus width. Disadvantageously, it becomes further difficult to design a substrate, an expense of the substrate is increased, and the number of pins for an ASIC (Application Specific Integrated Circuit) is increased.
Accordingly, various discussions have been made in order to solve the above-described problems. Currently, a high-speed transmission method by a point-to-point connection and a packet switch technology is considered. Thus, standards such as HyperTransport™, Rapid I/O™, fiber channel™, InfiniBand™, and the like are specified.